Vocabulary. sequential - последовательныйreview - обзор include - включать sequential - последовательный mining construction - горное строительство well-proven - хорошо зарекомендовавшей себя accommodate - вмещать adopt – внедрять, принимать overlapping - совмещение carry out - осуществлять similar - аналогичный bulk excavation - объёмное копание, объёмное рытье undertake - предпринимать road deck - пролётное строение моста disruption - нарушение environmental impact - воздействия на окружающую среду dust - пыль explosive - взрывной drilling rig - буровая установка designated - назначенный depth - глубина detonator - детонатор waste - отходы hence - следовательно measure - измерять duration - продолжительность appropriate - соответствующий equipment - оборудование competent rock -крепкая порода; твёрдая порода TBM - туннелепроходческая машина rock cutter - резец породный roadheader - проходческий комбайн grouting - закрепление грунтов freezing - замораживание relocate - передислоцировать
Methods of tunneling vary with the nature of the material to be cut through. All the tunnelling techniques reviewed for possible use include cut and cover, drill and blast, bored tunnelling and sequential mining construction. 1. Cut and Cover Tunnelling. Cut and cover tunnelling is a common and well-proven technique for constructing shallow tunnels. The method can accommodate changes in tunnel width and non-uniform shapes and is often adopted in construction of stations. Several overlapping works are required to be carried out in using this tunnelling method. Trench excavation, tunnel construction and soil covering of excavated tunnels are three major integral parts of the tunnelling method. Most of these works are similar to other road construction except that the excavation levels involved are deeper. Bulk excavation is often undertaken under a road deck to minimise traffic disruption as well as environmental impacts in terms of dust and noise emissions and visual impact. 2. Drill and Blast. This tunnelling method involves the use of explosives. Drilling rigs are used to bore blast holes on the proposed tunnel surface to a designated depth for blasting. Explosives and timed detonators are then placed in the blast holes. Once blasting is carried out, waste rocks and soils are transported out of the tunnel before further blasting. Most tunnelling construction in rock involves ground that is somewhere between two extreme conditions of hard rock and soft ground. Hence adequate structural support measures are required when adopting this method for tunnelling. Compared with bored tunnelling by Tunnel Boring Machine (see below), blasting generally results in higher but lesser duration of vibration levels. A temporary magazine site is often needed for overnight storage of explosives. 3. Bored Tunnelling. Bored tunnelling by using a Tunnel Boring Machine (TBM) is often used for excavating long tunnels. An effective TMB method requires the selection of appropriate equipment for different rock mass and geological conditions. The TBM may be suitable for excavating tunnels which contain competent rocks that can provide adequate geological stability for boring a long section tunnel without structural support. However, extremely hard rock can cause significant wear of the TBM rock cutter and may slow down the progress of the tunnelling works to the point where TBM becomes inefficient and uneconomical and may take longer time than the drill-and-blast tunnelling method. 4. Sequential Excavation Method. This method is also known as the New Austrian Tunnelling Method (NATM). The excavation location of a proposed tunnel is divided into segments first. The segments are then mined sequentially with supports. Some mining equipments such as roadheaders and backhoes are commonly used for the tunnel excavation. The ground for excavation must be fully dry for applying the NATM and ground dewatering is also an essential process before the excavation. Another process relates to the ground modifications such as grouting, and ground freezing is also common with this method in order to stabilize the soil for tunnelling. This method is relatively slow but is found useful in areas where existing structures such as sewer or subway could not be relocated.
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